RNA viruses are viruses having RNA as their genomes. Here, the RNA viruses have (+)-stranded RNA (positive sense RNA), complimentary (−)-stranded RNA (negative sense RNA), or double-stranded RNA, which is transcribed into mRNA, as their genomes. The (+)-stranded RNA may be translated to produce proteins when host cells are infected with the (+)-stranded RNA, and the (−)-stranded RNA is converted into (+)-stranded RNA by RNA polymerase, and then translated to produce proteins.
Therefore, an infection rate is high in the case of viruses having (+)-stranded RNA. Also, since RNA viruses have RNA as their genomes, there is no proof-reading done by DNA polymerase, which leads to a significant increase in mutagenesis compared with DNA viruses. As a result, new RNA viruses, such as SARS, hepatitis C, and polio, which cause diseases in humans, continue to appear, and there is a limit in producing vaccines against the new RNA viruses. In recent years, commercially available antiviral agents include nucleoside derivatives such as iododeoxyuridine (IDU), acyclovir (ACV) or azidothymidine (AZT), or proteins such as interferon (IFN). However, various side effects of the antiviral agents, for example, cytotoxicity, hepatotoxicity and drug resistance, have been reported. Therefore, there is a demand for development of a therapeutic agent for preventing or treating viral infections which has superior effects and few side effects.
Meanwhile, Tetracera scandens is a flowering plant which belongs to the Dilleniaceae family and grows mainly in Vietnam, and much research on its medical effects is being conducted. For example, it was reported that T. scandens has a pharmacological effect on an inflammatory response (Biol. Pharm. Bull. (2004) 27: 1414), and it was disclosed that a 4H-chromen-4-one derivative included in an extract of T. scandens serves to enhance glucose intake (Korean Patent No. 10-0979459). However, there is no report that T. scandens shows an antiviral effect by inhibiting reverse transcriptase activities of RNA viruses.